The present disclosure relates to a communication apparatus and particularly to a communication apparatus that uses a satellite navigation system such as a GPS (global positioning system).
In a GPS (global positioning system), by Doppler effect associated with a movement of an artificial satellite (hereinafter, referred to as GPS satellite) or a communication apparatus that receives a signal (hereinafter, referred to as a GPS signal) from the GPS satellite, a frequency of the GPS signal received by the communication apparatus varies, that is, a Doppler shift is generated. Due to the Doppler shift, there is a fear that accuracy of synchronous acquisition of the GPS signal performed by the communication apparatus may degrade.
In view of this, in related art, there has been proposed that a sampling frequency of an A/D converter that performs A/D conversion for a GPS signal in consideration of an error of an internal clock or a Doppler shift amount is set, thereby correcting a deviation of a chip rate of a C/A code used for spectrum spreading of the GPS signal (see, for example, Japanese Patent Application Laid-open No. 2005-204079).
Further, in related art, to increase accuracy of the synchronous acquisition, coherent addition is repeatedly performed for GPS signals on a predetermined bit basis, and correlation calculation between the coherent addition calculation result and a C/A code generated in a communication apparatus is performed, thereby increasing a detection sensitivity for a peak of the correlation calculation.